Silicated separator and process of making the same



R. CA BENNER SILICATED SEPARATOR AND PROCESS OFy MAKING THE SAME Filed March 28. 1925 z" .ZJ

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I 1 j n Patented May 27, 1924.

VUNITED s TATEs 1,495,568 Pa'rlszN'r OFFICE.

RAYMOND BENNER, F BAYSIDE, NEW YORK, ASSIGNOR TO UNION CARBIDE 8a 'CARBON RESEARCH LABORATORIES, INC., A CORPORATION 0F NEW YORK.

SILICATED SEPARATOR tAND PROCESS 0F MAKING THE SAME.

Application filed'Maroh 28, 1923. Serial No. 628,376.

To all whom it may concern.'

Be it known that I, RAYMOND C. BENNER, a citizen of the United States, residing at Bayside, in the county of Queens and State of New York, have inventedv certain new and'useful Improvements in Silicated Separators and Processes of Making the Same, of which the following is a specification.

This invention relates to improvements in bonded fiber separators for the electrodes of galvanic cells, particularly storage cells in which the electrolyte is a solution of sulfurie acid. I

In my application Serial No. 530,943, filed January 21, 1922, of which the present is a continuation-in-part, I have described and claimed separators formed by fabricating sheets of fibrous material and impregnating the sheets with a soluble silicate. Upon 90 immersing the impregnated separators in sulfuric acid electrolyte, gelatinous silicio l acid is precipitated throughout the body of the separator. The siliceous gel may -be formed byf any suitable means before inserting the separator in the battery, but in such case the 'separator must not be allowed to dry. Silica gel is an irreversible colloid and if dehydrated by drying it will not again take up water. Silicated separators have 3 numerous advantages, notably substantial immunity to oxidation by contact withthe positive electrode. An object of the present invention is to provide means for increasing the porosity and strength of. silicated fiber 35 separators, so as to enable them to give still more effective service. An additional feature of the invention is the use, as the impregnating agent, of a silicate forming an insoluble `sulfate or other insoluble com- 40 pound. K

Reference is .to be made to the accompanyini` diagrammatic drawing, in whichig. 1 is a front elevation of a silicated separator containing soluble and insoluble 5 fibers; y

Figs. 2 and 3 are similar views vshowing' resipectlvely separators containing bulky sti ening agents and lon fibers;

Figs. 4 and 5 are vertlcal transverse sections throu h composite separators; and

Figs. 6, and- 8 are similar views showing separators having wear-resistant inserts therein. l

Referring to Fi 1 of the drawings, reference numeral 1 enotes a separator sheet bonded with a silicate and in this instance containing soluble and insoluble fibers 2,

It has been found that for some purposes the presence of silicic acid may make the resistance of the separators rather too high. According to the present method this may be avoided by incorporating an electrolytesoluble material, preferably fibrous as illustrated, with the insoluble fiber. Upon solution of this material the porosity of the separator is increased, with a corresponding decrease of resistance. i x

The preferred electrolyte-soluble substance is the material known as cotton linters. This dissolves with relative ease in sulfuric acid, giving the desired porosity. The channels formed -by its removal are tortuous and of small diameter, however, .so that no opportunity is given active material to pass through the separator.

The strength and stiffness of'silicated fiber separators may be increased by adding relatively large pieces of suitable material to the fiber before working it up into sheets (Fig. 2). Sulfite screenings or other materials formed in ways which. remove substances .which might be harmful to the battery, are

particularly suited for this purpose. Sulfite screenings are slivers of wood, indicated by numeral 3, which have been subjected to the Sulfite process but have resisted conversion into pulp.

I have used with advantage screenings averaging about ig to in length and having a diameter of about 312 or less, but the size may vary within wide limits. The material as it comes on the market consists-of a major portion of slivers associated with' some fibers. It may be used in this condition for fabricating sheets to be silicated, or a further amount of fibers may be added. Separators containing screenings or the like have increased strength and retain their stiffness, after treatment with acid, some-` what lbetter than when fibers alone are 10 I present.

As an alternative to the use of bulky stiflening materials, such as the screenings just referred to, acid-resistin fibers of considerable length may be ad ed to increase 1, the strength of the separator, as shown at 4, Fig. 3. In preparing separators for use in internal combustion motor starting batteries andother purposes, where strength and low resistance are required, it has been 11 y found, in some cases, that inthe attempt to secure increased strength by compacting sulfite pulp ti'bers unde-r heavy pressure the resistance has been unduly raised. rlihis dilliculty may be avoided by incorporating with the short pulp fibers a suitable proportion of. long-fibered material, which may for example be glass Wool, hair or other acid-resisting organic or inorganic liber. The strength is increased in this manner without a proportionate increase in the resistance, since it is unnecessary to resort to compacting under heavy pressure. rllhe long bers are securely anchored in the binder, which is not always the case with short.- tibered material. Y

rllhe amount of long y fibers may vary widely. Good results have been obtained with an intermixture of equal parts by weight of pulp bers and glass Wool, hair. or other acid-resistant liber.

In some cases sheets or layers 5 of longfibered material may be placed on one or both sides ot a sulte ulp separator 6, Figs. t and 5. llt ispre erred to make the composite separator substantially integral. as by .impregnating the wholev with a soluble silicate. The sheets may. however. be merely placed in contact. with or without impregnation. lin my application Serial No. 593.427. tiled @ctober 9, 1922, ll have described and claimed somewhat similar composite separators. The present invention is distinguished principally by the use ot long fibers.

Strengthening materials ot the kinds indicated in the tore-going description may be added to separators composed ot sulfite pulp fibers or other inert bers only. but they are especially advantageous in those which contaui also electrolyte-soluble substances. SuchA substances may be fibers, volatile or soluble salts, or the like.

ln Figs. 6, T. and 8 separators having` ,Wear-resisting inserts are shown. rll`hese may be formed by pertorating the separator and inserting in the perforation a sulicient amount ot a plastic material to extend to or beyond the bounding` planes ot the separator. Fig-6 shoWswear-resistant inserts 'i' flush with the surface ot the sheet. Figs. 7 and 8 illustrate protruding inserts 8 and 9. the latter having heads 10. The inserts are preferably formed ot plastic material, for example rubber, acid-resistant phenolic condensation products. or the like. They are secured to the body of the separator by union ot the plastic material with the adjacent portion of the separator. For example, when plastic rubber is placed in the separator'perforations and compressed and heated in the vulcanizing process, a portion of the rubber enters the walls of the perforations and is hardened there, forming a bondor anchorage for the insert. When menace headed inserts are used this bonding action 'is not solely depended upon to retain them,

sirability'of Vspacing the separators from the plates, the headed or protruding type ot insert is preferred. c c

' l have found that it is advantageous for some purposes tolav'oid the use oitsoluble silicates in impregnating the separators. lf the precipitation of silicio acid is effected in the battery, as is most convenient, soluble salts are formed in the electrolyte, for example sodium sulfate when sodium silicate lis the impregnating agent. To avoid this, a silicate which will form an insoluble sulfate may be used. .Barium silicate is the preferred salt. llt may be applied to the separator in any suitable way, as by admixture with the'librous material before fabricating it-' intosheets, or theseparator may be impregnated with ay soluble silicate and then treated with a soluble barium salt. lln the latter case 'the soluble reaction product should be washedV out. When separators containing barium silicate are immersed in sulfuric acid electrolyte, silicio acid and barium sulfate are precipitated throughout the body of the separator. lhe presence or the insoluble sulfate does not result in objectionable increase of resistance.

'llhe separators may be ribbed. shaped into tubular form, or given other conformations desirable .for particular conditions. Various other departures from the specific forms shown may be made `Within the scope of the invent-ion .as dened in the appended claim.

l claim:

1. separator comprising a fabricated sheetr of fibrous materials, one of which is disintegrated by sulfuric acid electrolyte, said sheet being impregnated With a substance capable of yieldinga gelatinous, acidproof decomposition residue'.

2. rll`he invention according to claim 1, in which .a 'strengthening materialY is incorporated in the` separator.

3. A separator comprising short-ibered material having relatively long reinforcing bodies commingled therewith, the Whole being-impregnated with a substance capable ot yielding a gelatinous, acid-proof decomposition residue.

d. The invention according to claim 3, in which the reinforcing bodies are enlongated wood t fragments.

5. A separator comprising ibrous materials, one of which is soluble in sulfuric acid res lll@

electrolyte. associated With relatively longer which the longer fibers comprise animal hair. v

7. A composite separator comprising a sheetl of relatively Weak material supported by a sheet formed from long, acid-resistant bers.

8. The invention according to claim 7, in

which the separator is impregnated at least in part With a substance capable of yielding a gelatinous, acid-proof decomposition residue.

9. A composite 'separator comprising a sheet of sulfite pulp fiberl supported by sheets formed from animal hair.

10. A separator comprising a sheet of material impregnated with a substance capable of yielding a'y gelatinous, acid-proof decomposition residue and of forming another insoluble compound.

11. The invention according to claim 10,v in Which the impregnating material is barium silicate.

l2. The invention according to claim 10,4 in which the sheet is -fabricated from fibrous material.

13. A' silicated separator having a plastic wear-resisting insert secured therein.

14. A silicated separator having a plastic Wear-resisting insert therein, said insert having an end overlying the surface of the separator.

15. Process of making separators comprising mixing With ibrous material a substance capable of formin -an acid-proof decomposition residue, an preparing sheets from the resulting product.

In testimony whereof lI afiix m si nature.

RAYMOND c. B N ER. 

